Extended room temperature storage of epoxy resins

Abstract

Uncured epoxy resin for use in making prepreg for aerospace applications. The resin includes an epoxy resin component comprising difunctional epoxy resin, trifunctional epoxy resin and/or tetrafunctional epoxy resin and a sufficient amount of [3-(4-aminobenzoyl) oxyphenyl]4-aminobenzoate (3-ABOAB), as a curing agent, such that the uncured resin can be stored at room temperature of at least 6 weeks and wherein the uncured resin can be fully cured in no more than 2 hours at a temperature of between 175° C. and 185° C.

What is claimed is: 
     
       1. A prepreg which can be stored at room temperature for at least 6 weeks and which can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C., said prepreg comprising:
 a fiber reinforcement; 
 an uncured resin comprising:
 an epoxy resin component comprising a trifunctional epoxy resin selected from the group consisting of triglycidyl-m-aminophenol and triglycidyl-p-aminophenol; and 
 a curing agent comprising a sufficient amount of [3-(4-aminobenzoyl) oxyphenyl]4-aminobenzoate such that the stoichiometric ratio between said epoxy resin component and said curing agent is between 0.65:1 and 1.1:0.8 and wherein said uncured resin can be stored at room temperature for at least 6 weeks and wherein said prepreg can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C. 
 
 
     
     
       2. A prepreg according to  claim 1  wherein said epoxy resin component additionally comprises diglycidyl ether of bisphenol F. 
     
     
       3. A prepreg according to  claim 2  wherein said epoxy resin component additionally comprises N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenyl methane. 
     
     
       4. A prepreg according to  claim 1  wherein the said uncured resin comprises a soluble thermoplastic and insoluble thermoplastic particles. 
     
     
       5. A prepreg according to  claim 4  wherein said soluble thermoplastic comprises polyethersulfone. 
     
     
       6. A prepreg according to  claim 5  wherein said insoluble thermoplastic particles comprise polyamide particles. 
     
     
       7. A prepreg according to  claim 1  wherein said epoxy resin component consists of triglycidyl-m-aminophenol and wherein the stoichiometric ratio between said triglycidyl-m-aminophenol and said curing agent is between 0.7:1 and 0.95:1. 
     
     
       8. A prepreg according to  claim 7  wherein the said uncured resin comprises a soluble thermoplastic and insoluble thermoplastic particles. 
     
     
       9. A prepreg according to  claim 8  wherein said soluble thermoplastic comprises polyethersulfone. 
     
     
       10. A prepreg according to  claim 9  wherein said insoluble thermoplastic particles comprise polyamide particles. 
     
     
       11. A prepreg according to  claim 2  wherein the said uncured resin comprises a soluble thermoplastic and insoluble thermoplastic particles. 
     
     
       12. A prepreg according to  claim 11  wherein said soluble thermoplastic comprises polyethersulfone. 
     
     
       13. A prepreg according to  claim 12  wherein said insoluble thermoplastic particles comprise polyamide particles. 
     
     
       14. A prepreg according to  claim 3  wherein the said uncured resin comprises a soluble thermoplastic and insoluble thermoplastic particles. 
     
     
       15. A prepreg according to  claim 14  wherein said soluble thermoplastic comprises polyethersulfone. 
     
     
       16. A prepreg according to  claim 15  wherein said insoluble thermoplastic particles comprise polyamide particles. 
     
     
       17. A composite material comprising a prepreg according to  claim 1  which has been cured. 
     
     
       18. A composite material according to  claim 17  wherein said composite material forms at least part of a primary structure of an aircraft. 
     
     
       19. A method for making a prepreg which can be stored at room temperature for at least 6 weeks and which can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C., said method comprising the steps of:
 providing an uncured resin which can be stored at room temperature for at least 6 weeks and which can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C., said uncured resin comprising:
 an epoxy resin component comprising a bifunctional epoxy resin selected from the group consisting of triglycidyl-m-aminophenol and triglycidyl-p-aminophenol; 
 a curing agent comprising a sufficient amount of [3-(4-aminobenzoyl) oxyphenyl]4-aminobenzoate such that the stoichiometric ratio between said epoxy resin component and said curing agent is between 0.65:1 and 1.1:0.8 and wherein said uncured resin can be stored at room temperature for at least 6 weeks and wherein said uncured resin can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C.; and 
 combining said uncured resin with a fibrous reinforcement to provide said prepreg. 
 
 
     
     
       20. A method for storing an uncured resin at room temperature for up to six weeks or more, said method comprising the steps of:
 A) providing an uncured resin which can be stored at room temperature for at least 6 weeks and which can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C., said uncured resin comprising:
 a) an epoxy resin component comprising a bifunctional epoxy selected from the group consisting of triglycidyl-m-aminophenol and triglycidyl-p-aminophenol; 
 b) a curing agent comprising a sufficient a count of [3-(4-aminobenzoyl) oxyphenyl]4-aminobenzoate such that the stoichiometric ratio between said epoxy resin component and said curing agent is between 0.651 and 1.1:0.8 and wherein said uncured resin can be stored at room temperature of at least 6 weeks and wherein said uncured resin can be fully cured in no more than 2 hours at a temperature of between 165° C. and 190° C.; and 
 
 B) storing said uncured resin for up to 6 weeks or more at room temperature.